Various heat transfer recording methods have been known so far. Among these methods, dye diffusion transfer recording systems attract attention as a process that can produce a color hard copy having an image quality closest to that of silver halide photography. Moreover, this system has advantages over silver halide photography: it is a dry system, it enables direct visualization from digital data, it makes reproduction simple, and the like.
In the dye diffusion transfer recording systems, a dye-containing heat-sensitive transfer sheet (hereinafter also simply referred to as “an ink sheet”) and a heat-sensitive transfer image-receiving sheet (hereinafter also simply referred to as “an image-receiving sheet”) are superposed, and the ink sheet is heated using a thermal head with which heat generation can be controlled by electric signals. Thereby a colorant (hereinafter also referred to as “a dye”) in the ink sheet is transferred to the image-receiving sheet to record image information. More specifically, a transferred color image with a continuous change in color shading can be obtained by recording three colors including cyan, magenta and yellow, or four colors including black in addition to the three colors in the manner of one over another.
Owing to a recent progress of computerized digital image processing technique, a quality of the recorded image is improving and a market of the dye diffusion transfer recording system is growing. In accordance with the growth of market, a demand for both speed-up of the print system and high density imaging is increasing.
Moreover, the need of a double-side print with a photographic quality is increasing from a demand for making of photo-books.
Heat-sensitive transfer image-receiving sheets for a double-side print have been proposed from the past (see U.S. Pat. No. 4,778,782, JP-A-64-47586 (“JP-A” means unexamined published Japanese patent application), JP-A-5-229265, JP-A-9-202057 and JP-A-2002-211142). However, these image-receiving sheets had problems such that image quality of one side is not satisfactory for photographic-image reproduction, and that these sheets are difficult in handling because if these sheets after being formed with a receptor layer are stored in a state wherein the front side of a sheet is in contact with the back side of another sheet, they would be adhered to each other. For example, in U.S. Pat. No. 4,778,782, JP-A-64-47586 and JP-A-5-229265, it has been suggested forming a sublimation type receptor layer on both sides. However, image qualities did not satisfy the demand. Further, there were problems in production. On the other hand, in JP-A-9-202057 and JP-A-2002-211142, it has been suggested sheets both sides of which can be printed. However, image qualities did not satisfy the demand for photographic image reproduction.